PROJECT SUMMARY/ABSTRACT Epileptic seizures can be characterized as concerted and synchronized activity of neurons across the brain for an extended period of time. We hypothesize that, as for other normal brain-controlled behavior, epileptic seizures are not caused by random activity of neurons, but rather arise from activity in a specific, organized brain network. Our overarching goal is to elucidate such a seizure-specific network in the brain and to deliver genetic neuromodulation specifically to such a seizure-generating network for tailored seizure suppression. In our proposal, we first identify all the critical brain cells that make up that seizure network in acute and chronic rodent models of epilepsy. Then, we will manipulate such a network to stop seizure occurrence. We will identify and visualize brain structures and cells responsible for generation of seizures in the whole brain by labeling these cells with a fluorescent protein tag utilizing sophisticated gene expression techniques in genetically modified mice (Specific Aim 1). This seizure-specific labelling of neurons occurs when they exhibit extensive activity in the presence of a chemical in the system during a seizure episode. This labelling procedure will be repeated to examine if the same neuronal populations become active in two separate episodes of seizures. The cells labeled with the fluorescence reporter will be examined by fluorescence microscopy. Overlapped labelling of neurons between two seizure episodes will support our hypothesis that the same subset of neurons is repeatedly involved in generation of seizures. We will then employ a similar strategy to deliver genetic neuromodulation to a seizure-generating network (Specific Aim 2). We engineered a viral vector that carries a molecular tool that suppress neuronal activity when an activating drug is injected into the animal. This viral vector will be injected into a brain region responsible for generation of seizures in the rodent models of epilepsy we will use. We expect that such manipulation will suppress subsequent seizures. Our hypothesis views and treats epileptic seizures as a network function in the brain. Together with robust network-specific suppression of seizures in mouse models of epilepsy, this will change the way we view and treat this disease.